Electrical musical apparatus



May 30, 1950 J. M. HANERT ELECTRICAL MUSICAL APPARATUS Filed March 8, 1946 Patented May 30, 1950 ELECTRICAL MUSICAL APPARATUS John M. Hanert, Park Ridge, Ill., assignoi` to Hammond Instrument Company, Chicago, Ill., a corporation of Delaware Application March 8, 1946, Serial No. 653,195

1 Claim.

My invention relates generally to electrical musical apparatus and more particularly to means for selectively introducing vibrato and chorus effects into electrical musical tone signals.

As more fully set forth in my prior Patent 2,382,413, a very desirable vibrato effect may be introduced into an electrical musical tone signal by transmitting the signal through an artificial line and effectively scanning the artificial line by a suitable pickup which operates to pick up the signal from spaced sections of the artificial line, in effect, in an oscillatory manner.

The effect produced is that of a true pitch vibrato in which the signal frequency is continuously being shifted either sharp or fiat with respect to the original steady input signal. This vibrato effect is musically characterized as being expressive of emotion and excitement. For music of a theatrical and orchestral nature the vibrato has proved its worth, as is shown by the universal acceptance of instruments such as the violin which are nearly always played in a, man.. ner to produce a vibrato of sustantial width.

However, there are other musical instruments, particularly the organ, in which the vibrato effect may be out of character when playing certain types of music, such as ecclesiastical or church music. The effect desired under these latter circumstances is not one of wavering pitch, but is rather one of a chorus of relative stable frequencies such as the chorus effect produced by a choir of voices or organ pipes. This latter musical effect, while productive of a warmth of tone, is nevertheless of a more steady character and the listener does not perceive any particular variation in pitch, but instead, perceives the pleasant eiect of several closely related frequencies sounding to make a chorus or celeste tone, as the effect is frequently termed in naming pipe organ stops. rlhis chorus effect, as differentiated from the vibrato effect, can be produced by providing a plurality of sources, such as two or three alternating current generators of slightly different pitch, or by the use of several mechanical generators, such as organ pipes or reeds of slightly diifering pitch. However, it is obvious that the production of the chorus effect by this means is very costly since it involves duplication or triplication of the entire generating apparatus to produce this one effect.

In the apparatus of this invention a chorus tonality is produced by the novel means and method of generating a relatively large series of side band vibrato frequencies (by which the tone is given the effect of a wavering pitch or vibrato) in combination with the original steady frequency. The inclusion of the original steady frequency along with the vibrato side band fre; quencies has the effect of removing the apparent shift in frequency which the vibrato alone produces, and the resulting effect, that of a chorus between the vibrato side band frequencies and the original frequency, is achieved. The width of the chorus thus produced is dependent upon the width of the vibrato. If the vibrato eifect is wide, that is, the frequency is being modulated sharp and fiat to a relatively great extent, the resulting vibrato when mixed with the unmodulated original steady frequency will simulate the effect of a chorus of tones in which the individual pitches are relatively widely separated, whereas when the vibrato deviation pitch factor is small, the chorus effect will also be small, and will correspond to a plurality of sources whose pitches are in a relatively narrow band. The inclusion of the unmodulated original signal is also very effective to mask the perception by the listener of the modulating periodicity of the vibrato effect, which usually is in the order of 5 to 7 C. P. S.

It is thus the primary object of this invention to produce a chorus effect in which but a single primary generator is employed together with a vibrato producing system, and apparatus for combining the two signals in approximately equal proportions.

A further object is to provide an improved method and apparatus capable of introducing a chorus effect in a musical signal vderived from any source and in which such effect is initially absent.

Other objects will appear in the following description, reference being had tothe accompanying drawing which constitutes a schematic diagram of a representative instrument.

As previously stated, the apparatus may be used selectively to introduce a combined chorus and vibrato effect or to introduce either of these effects in musical tone signals derived from any source, such as an organ, represented by the block 20 in the drawing. The signals produced aby the source 20 are amplified in a preamplifier 22 and the amplified signal impressed across a voltage dividing network, comprising resistors R24, R25 and R26, by conductors 28 and 29. The conductor 28 is illustrated as being connected to ground and is connected to a conductor 30 by a resistor R32. The conductor 28 may be connected to the conductor 29 through a compensating resistor R34 upon moving a switch 36 to its full line position. The switch 36, when moved to its dotted line position, shunts resistor R32 by connecting conductor 28 directly to conductor 30 arr also disconnects the compensating resistor R A multi-section articial line, comprising a plurality of series inductances L38 and shunt capacitors C4D, has the signal supplied by the preamplifier 22 impressed across its input terminals. A plurality of conductors I to I5 are connected to spaced points along the articial line. It will be noted that conductors 9 to I4 inclusive are connected between a pair of series voltage dividing capacitors C42 .and C43 and are also connected to the conductor 3D through `resistors R44 to prevent the accumulation of static charges on these conductors.

The termination of the articial line comprises a series inductance L46 in parallel with a capacitor C48, these elements being connected to the conductor 30 through a termination capacitor C54] having a terminating resistance R52 in parallel therewith.

As kmore fully disclosed in my Patent No. 2,382,413, there is provided a plurality of iixed circumferentially spaced capacitor segments A(i3 to 1.5 inclusive. A pickup or scanning vcapacitor plate I3 is rotated at a `speed :in the 'order of `5 to '7 R. P. S. so as successively to be .incapacitative pickup relation with the various :seg-ments 6D to 15.

The segment 6I! is connected to .conductor I5., the segments 4ISI and 62 to a conductor ensegments 53 `and 4.64 to conductor vb, t5 and 65 to fc. B1 and 68 to d, 69 and 'I0 to e, 'II .and :l2 to j, 'I3 and 14 to g. while-segment 'I5 has a conductor h connected thereto.

There are three manually 'operable' multiple switches provided to connect conductors a to h. to conductors I to i4 in predetermined combinations. These switches are illustrated as being manually operable by push buttons Bt, ill and 3,2 respectively to cause the apparatus to produce a wide a medium or a narrow vibratore,- fect. Each oi the push buttons mi tc 32 upon operation closes a series of eightsingle pele single "throw switches 83. It will be noted that operation of the push button 33 connects conductors 2, 4'. 6, 9, II, I2, I3 and. I4 to conductors a to h respectively.' Depression of the push -button 8! connects conductors I, 3, d, 5, 3, 9. Il) and H t@ conductors a tn h respectively. den-resH sion of the push'button 82 connects conductors I to 8 tc conductors ato h respectively.

The signal pickup plate 'I8 has a shielded'coni ductor 83 connected thereto, which, upon `closure of a manually operable switch 81, is connected with the junction between resistors R25 and R26 of the Voltage divider. Conductor 3E is also connected tothe input of a pentode 83 which operates as a triode, the input circuitincluding a blocking capacitor C911, and a radio frequency eliminating resistance R92. The cathode 94 of this tube is connected to lground through sel-fbias resistor R94 and a load resistor R95'. `The junction 93 between these resistors is connected tothe grid 98 of a triode It!) through a lblocking capacitor CIIiZ and a vseries grid resistor RI 34. A static chargepreventing resistor RIEJ is connected' between the conductor 86 and resistor RIM. The plate Iil of pentode 88 is connected to a suitable source of ,plate potential, indicated as +B, through a load resistor RI il), `and-is connected to the grid IIZ of a triode II4 through a blocking capacitor CIIB. The grids `98 and I'I2 lareconnected to Aground through resistors RI i'! 4 and RI I8. 'I'he cathodes of the triodes |00 and II4 are connected to ground through a common self-biasing resistor RI20. The plates of triodes I 00 and II4 are respectively connected to the terminals of the primary winding of a transformer TI22, the center tap ofV which is connected to a suitable source of plate current, indicated as a terminal +B. The secondaryl of the transformer TI22 is connected to a power amplier |24, and the output of the latter is supplied to a speaker |26.

When it is desired to introduce a wide vibrato effect into the music being rendered, Without any chorus eiect,jthe switch YIii) is placed in its dotted line position and push button 8B is operated to close its switchesI 83, thereby connecting the conductors 2, 4, E, 8 II, I2, I3 and I4 to conductors a to h respectively. It will therefore be noted that asthe pickup plate 'I8 rotates, it will successively pick up the signal commencing at one end of the artificial line, traversing the line in steps of 2, 3, 3, 4, 4, 3, 3, 2 sections of the artificial line and then retraversing the line in the reverse direction. At high frequencies the amount of phase shift between adjacent scanning positions is considerably in excess of 180 and therefore a multiple rate tremulant, or amplitude modulation eiizect, is produced at these very high frequencies. The periodicity of this tremulant ef- -fect vis masked by making the degree of phase shift ybetween scanning positions of unequal eX- tent.

When it it desired to introduce the vibrato eiiect into Vthe music being rendered, the switch 81 is opened, whereas when no vibrato effect whatsoever is desired this switch is closed. Under the latter conditions the signal appearing across 'the resistor R26 is impressed on the grid of pentode'. Since the impedance of this circuit is low compared to that which includes the capacitorplates 60 to 15 andr scanner plate "I8, the signal picked up by the scanner plate 'IB is comparatively negligible. .In effect, the output of the preampliiier 22., as reduced in amplitude by the voltage dividers R24, R25, R25, is impressed directly upon the input of the pentode 88.

When itis desired to produce a wide vibrato `effect the switch 8'! is opened and .the switch 35 moved to its dotted line position. Under these circumstances the resistor R32 is shunted out of the circuit and the output signal of the pream- 4plii-ler 22 is connected directly to the input end Yvibrato effect is obtained when the push button is depressed, since the latter connects the conductors 2, 4, 6, 9, il, I2, I3 and I4 to the conductors a to h respectively. Thus the scanner plate 'lpicks up the signal from the full length of the artificial line. rst in one direction and then returning in an eiectively oscillator manner at .the scanning periodicity of 5 to 'l C. P. S.

When a wide vibrato chorus effect is to be obtained, the switch 8i is left open, push button 8l] depressed and the switch 33 moved to its full line position. Under these circumstances the vibrato eiiect is produced in the same manner as described in the preceding paragraph except that the resistor R32 is no longer shunted cut ofthe circuit, but instead, is connected between `conductors 28 and V3i). For the signal developed across the resistor R32 the capacitors Csi?, C42.'

all in parallel, constitute a negligible impedance. Thus the output signal of the preamplier 22 which appears across the resistor R32 will also appear between the grounded conductor 28 and the conductors l to l inclusive and thus will appear upon the segmental capacitor plates 88 to l5 without substantial phase alteration, and will be picked up by the scanner plate 'I8 and impressed upon the input of pentode 88. The value of resistor R32 is such as to produce an unmodulated signal of substantially the same amplitude as the modulated vibrato signal which is also supplied to the input of pentode 88. The effect produced is that of the steady frequency signal plus a large number of side band frequencies, due to the vibrato signal, and this may best be characterized as a chorus effect since the listener perceives it as tones produced by a large number of instruments playing in chorus. The steady frequency component of the output signal masks the slightly wavering effect of the vibrato signal. The combined signal is thus perceived as a pure chorus effect.

When a medium width vibrato is desired the push button 88 is released and the push button 8l depressed. With the switch 81 open, the switch 36 in its dotted line position, the operation ofthe apparatus will be similar to that previously described for the wide vibrato except that it will be noted that conductors l, 3, 4, 5, 8, 9, Il] and li will be respectively connected to conductors a to h, and that thus only a portion of the artificial line will be scanned. When a medium chorus effect is desired the switch 36 is shifted to its full line position and the operation of the apparatus will be similar to that above described with reference to the wide chorus effect, except that, due to the fact that only a portion of the artificial line is scanned, the number of side band frequencies due to the vibrato component of the signal will be reduced.

In a similar manner when only the push button 82 is depressed the conductors I to 8 will be connected to conductors a to h respectively, and a still smaller portion of the artificial line will be scanned. The num-ber of side band frequencies introduced Iby the vibrato component of the signal will be still fewer, with the result that either a very narrow vibrato effect or a very narrow chorus effect may be produced, depending upon the position of the switch 36.

From the foregoing it will appear that by the addition of very simple circuits and controls the apparatus shown in my aforesaid Patent No. 2,382,413 is made capable of producing various degrees of chorus effects which could otherwise be obtained only by the use of multiple generating systems. For example, to obtain an effect corresponding to the Wide chorus effect, without the utilization of the present invention, would require the addition of 10 or 12 complete generating systems (one generator for each note within the gamut of the instrument) while to produce an effect equivalent to the medium chorus eifect it would .be necessary to add about six generating systems, while to produce the narrow chorus effect it would be necessary to provide at least two additional generating systems.

The invention therefore provides an extremely simple solution for the problem of producing various degrees of chorus effect without requiring any alteration or additions to the generating system. Since the chorus effect producing apparatus is independent of the character of the tone signal generating system, it will be clear that the apparatus may be used with |benefit, irrespective of the source of the musical signal supplied to the preamplifier 22. The apparatus may thus be used with any musical instrument in which the output appears as an electrical signal, such as instruments of the electric organ class, electrical instruments of the melody type, as well as any other electrical musical signal sources. It might be pointed out that among the latter the signal source might be a microphone picking up the sounds produced by mechanical musical instruments which do not produce the vibrato effect. For example, the sounds produced by a piano or trombone might be picked up by a microphone and supplied to the preamplifier 22. The result would be that the output of the speaker 28 might be made to simulate a chorus of pianos or trombones.

While I have shown and described a particular embodiment of my invention, it will be apparent to those skilled in the art that numerous modifications and variations may be made in the form and construction thereof, without departing from the more fundamental principles of the invention. I therefore desire, by the following claims, to include within the scope of my invention all such similar and modied forms of the apparatus disclosed, :by which substantially the results of the invention may be obtained Iby substantially the same or equivalent means.

I claim:

In an electrical musical apparatus for introducing chorus effect into an electrical musical signal derived from a source incapable of producing an appreciable vibrato effect, the combination of an artificial line having its input coupled to the source, the artificial line having a plurality of terminals distributed along its length, scanning means for picking up the signal appearing at said terminals in an effectively oscillatory manner at a vibrato periodicity, means for selectively combining with the signal picked up by the scanning means a signal of substantially equal amplitude derived directly from the source, said last-named means comprising a twoposition switch and an impedance mesh to cause the output signal to be of substantially the same amplitude when the signal from the source is combined with the signal from the scanning means as when only the signal from the scanning means is utilized, and means for amplifying the output signal and translating it into sound, thereby to produce a chorus effect when the switch is in one position and a vibrato effect when the switch is in the other position.

JOHN M. HANERT.

REFEREN CES CITED The following references are of record in the file of this patent:

'UNITED STATES PATENTS Number Name Date 2,145,332 Bedford Jan. 31, 1939 2,221,188 Hammond et al. Nov. 12, 1940 2,245,354 Mroz June 10, 1941 2,287,105 Kannenberg June 23, 1942 2,382,413 Hanert Aug. 14. 1945 

